1. Field of the Invention
This invention relates to an electronic level and specifically to the visual display and calibration of the level.
2. Description of the Prior Art
Electronic levels known in the art include that sold by Wedge Innovations Inc. and as disclosed in U.S. Pat. No. 4,912,662 issued Mar. 27, 1990 to Butler et al. (assigned to Wedge Innovations Inc.). Furthermore, such prior art electronic level displays show the inclination in degrees or percent slope, which are typically not the inclination measurements used by building tradesmen (carpenters, masons etc.).
Butler et al. also disclose at col. 9, lines 6-11:
The rise/run mode 122 is determined by first using the determine angle routine of block 146 and the display routine of block 148. The display function is calculated at twelve times the tangent of the angle determined by block 146. This gives the rise to run value of inches per foot.
Prior art devices thus often do not provide a satisfactory indication of how far from level or plumb one is in a mode useful to tradesmen who tend not to think in terms of inches per foot or percent slope or angular slope.